     (fn [game group]
       (let [ world (.world game)
              pos (.position group)
-             possible-destinations (filter #(pos-free? game %) (land-cells-around world pos migration-radius))]
+             possible-destinations (filter #(pos-free? game %) (land-cells-around world pos (migration-radius group)))]
         (if (empty? possible-destinations)
           0.0
           (let [p (prosperity-in-pos game group pos)

    [civs.logic.demographics :refer :all])
  (:import [civs.model.core Population Tribe]))

(def migration-radius 3)

(defn- discovery-population-factor [total-pop required-pop]
  (+ 1.0 (Math/log10 (/ (float total-pop) required-pop))))

      (let [ world (.world game)
             pos (.position group)
             _ (check-valid-position world pos)
             possible-destinations (filter #(pos-free? game %) (land-cells-around world pos (migration-radius group)))
             preferences (map (fn [pos] {
                                     :preference (perturbate-low (prosperity-in-pos game group pos))
                                     :pos pos
